Physiology and psychology cover, between them, the field of vital phenomena; they deal with the facts of life at large, and in particular with the facts of human life.
Physiological psychology, on the other hand, is competent to investigate the relations that hold between the processes of the physical and those of the mental life.
Physiology is concerned with all those phenomena of life that present them selves to us in sense perception as bodily processes, and accordingly form part of that total environment which we name the external world.